Nonpositional line signal



1948. J. G. MITCHELL NONPOSITIONAL LINE SIGNAL Filed Oct. 2, 1945 FIG.1.

FIG. 3.

FIGZ.

INVENTOR JAY G. MITCHELL ATTORNEY Patented Oct. 5, 1948 UNITED STATESPATENT OFFICE NONPOSITIONAL LINE SIGNAL Jay G. Mitchell, Eatontown, N. Jassignor to the United States of America as represented by the Secretaryof War 4 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

The invention relates to a, non-positional drop or signalling device foruse in telephone switch boards and similar equipment to indicate thereceipt of an alternating current signal from a magneto generator or thereceipt of a direct current signal, as in common battery signallingsystems.

Heretofore, the operation of electrically operated mechanical signals ofthis general class has depended, for the display of a visual signal, onthe effect of gravity, thereby limiting the application of such devicesto situations Where the normal position of the signalling part isupright and rendering impossible their operation whenplacedhorizontally, upside down, or in such position that gravity could not beutilized to efiect its display when released.

It is therefore an object of this invention to provide an indicatingdevice that, when actuated by an electric current, will operate in anyposition, thereby being made suitable for equipment used in rough opencountry or in rapidly moving and unstable locations, such as in mobileequipment.

It is also an object of the invention to provide an operative electricalindicator which is light in weight, small in size and simple and.inexpensive to manufacture.

For a better understanding of the invention, reference is made to thefollowing description of one device embodying the invention, the saiddescription to 'be read in connection with the accompanying drawings, inwhich Figure 1 is a plan view of a device embodying the invention, and

Figure 2 is a cross sectional view of one feature of the device shown inFigure 1, and

Figure 3 is a front view of the feature shown in in Figure 2.

Referring to the drawing, a soft iron core piece 59, carrying a winding12, is provided at either end thereof with a pair of U-shaped, forwardlyextending, soft iron pole pieces l4, l6. These pole pieces l4, it areaffixed to the core piece In by means of screws [3.

The rearward pole piece I4 is preferably of greater length than theforward pole piece It, and is connected, at the ends thereof, to a pairof soft iron armatures :28 thru a pair of leaf springs 22. The springs22 are preferably of phosphur amended April 30, 1928; 370 O. G. 757)bronze, and are, aifixed to the pole piece l4 and the armatures 20- bymeans of screws 24.

The armatures 23 extend forwardly of the ends of the pole piece i6 andcarry a pair of shutters 26, 28 which are fastened to the armatures '20in any well known manner. The heads of set screws 38 retain thearmatures 20 and the shutters 26 in position against the pressureexerted by springs 22. The shanks of set screws 30 loosely fit into theapertures in shutters 26 and armatures 20 as indicated in Figs. 1 and 2.Shutters 26 and armatures 20 are slideable upon the shanks of set screwssince as is evident in Fig. 1 and Fig, 2-, the apertures in shutters 26and armatures 30 are larger than the screw shanks. Set screws 30 arealso utilized to adjust the lengths of the air gaps Ali between thearmatures 29 and the pole piece i6.

The forward shutter 26 is provided along its length with a plurality oftransverse slots 32 and the rearward shutter 28 is provided with aplurality of transverse colored markings 34, the said slots 32 andmarking 34 corresponding in size and number.

Referring now to Figures 2 and 3, the relativ position of the shutters26, 28 is shown when the indicating device is in its non-operatedposition. The slots 32 and the marking 34 are misaligned and the device,when normal, presents a solid color when viewed from the front,

As will be hereinafter pointed out, an incoming signal will causerelative movement of shutters 26, 28, whereby the slots 32 and themarking 34 will be aligned. The operated device will then display acolor when viewed from the front, which display of color indicates thata signal current has been impressed on the line.

The shutters 2t, 28 are provided on their opposing faces with a pair ofnotches 36, to hold the shutters in their operated position untilreleased by the operator.

As heretofore stated, the core piece W, the pole pieces l4, l6 and thearmatures 20 are formed of soft iron, thereby forming parallel magneticpaths characterized by low residual magnetism. Two small air gaps 33occur between the ends of the pole piece It and the armatures :20, andtwo adjustable air gaps M3 lie between the armatures 2t and the polepiece It.

Assume that an alternating signal current from a telephone line (notshown) is impressed upon the winding 2. The resultant induced magneticfield, depending upon the momentary direction of the impressedalternating current, will follow 3 the path indicated by the arrows 42(Figure 1). As the momentary direction of the alternating currentchanges, the path of the magnetic flux would be reversed as indicated byarrows (not shown) pointing in the opposite direction from the arrows42.

This rapid change of direction of magnetic flux is possible due to thefact that the device has been formed of soft iron characterized byhaving very low residual magnetism. Due to the fact that the air gaps 38are small, and due to the further fact that the air gaps is are inparallel arrangement, the resistance of the entire magnetic path issmall. The set screws 3:] enable the air gaps 40 to be adjusted foroptimum length for different operating conditions.

It may thus be seen that this device is operative upon application ofalternating current as well as application of direct current. The endsof pole piece i6, momentarily magnetic north poles, would attract theadjacent armature 29, momentarily magnetic south poles. As the directionof the alternating current reverses, the polarities will correspondinglychange and the armatures 20 will again be attracted by the pole piecel6. Although there may be a momentary slight chatter when alternatingcurrent is used, the notches 35 become engaged almost immediately,locking the shutters 26, 28 in place and causing the colored markings 34to be viewable through the slots 32, thus indicating to the operatorthat a signal has been impressed upon the line.

Any suitable means may be used to unlock the shutters in order to returnthe device to its nonoperative position. In current commercial telephonepractice, a plug is inserted into a jack in order to complete alistening circuit when a signal is indicated on a switchboard. Thesejacks are provided with an extra spring arm to return the presently usedgravity drop to position. With a simple modification, this extra arm maybe adapted to insert a wedge of proper contour between shutters 26, 28,thereby unlocking the device and allowing it to return to itsnonoperated position.

The device above described represents but one embodiment of theinvention, and it is obvious that many modifications and changes may bemade. The full scope of the invention is pointed out in the followingclaims.

What is claimed is:

1. A non-positional signal device comprising electromagnet means,armature means actuated upon the energization of said electromagnetmeans by a signal current and indicating means comprising apair ofshutters mounted in constant parallel relationship on said armaturemeans, at least one of said shutters being actuatable by said armaturemeans.

2. A non-positional signal device comprising a magnetizable core piece acoil positioned about said core piece, a forwardly extendingmagnetizable pole pieces afiixed to each end of said core piece therearward pole piece being of greater length than the forward pole piecea pair of forwardly extending magnetizab-le armatures fixed to the endsof the rearward pole piece through a pair of non-magnetic leaf springs,whereby the forward pole piece is spaced from the forward ends rearwardone of said shutters, and a plurality of transverse slots correspondingin number and size to the said markings formed in the forward of saidshutters and normally misaligned with said markings, and a pair oflocking notches formed on the opposing faces of said shutters wherebythe said shutters may be locked in operative position.

3. A non-positional signal responsive indicating device comprising a,magnetizable core piece having a winding disposed thereabout, a polepiece positioned at either end of said core piece, a pair of armaturesresiliently connected to the ends of one of said pole pieces, the freeends of said armatures being spaced from the ends of the other polepieces and being within the magnetic field generated about said otherpole piece, and indicating means carried by the free ends of saidarmatures whereby movement of said armatures will be translated intomovement of said indicating means.

e. A non-positional signal responsive indicating device comprising acore piece, a coil positioned about said core piece, a forwardlyextending pole piece affixed to each end of said core piece, a pair offorwardly extending armatures fixed to the ends of the rearward polepiece through a pair of nonmagnetic leaf springs, whereby the forwardpole piece is spaced from the forward ends of said armatures by a pairof air gaps in parallel arrangement, a pair of set screws disposedthrough the ends of said armatures and threadably connected to saidforward pole piece, whereby the lengths of said air gaps maybe adjusted,a pair of overlapping parallel shutters fixed to the forward ends ofsaid armatures and substantially at right angles thereto, a plurality oftransverse markings arranged along the forward face of the rearward oneof said shutters, and a plurality of tranverse slots corresponding innumber and size to the said markings formed in the forward of saidshutters and normally misaligned with said markings, and a pair oflocking notches formed on the opposing faces of said shutters wherebythe said shutters may be locked in operative position.

JAY G. MITCHELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 15,584 Lincoln Apr. 24, 1923735,953 Dean Aug. 11, 1903 914,235 Brown Mar. 2, 1909 1,318,792 NewellOct. 14, 1919 1,998,072 Blake et al Apr. 16, 1935 2,245,493 Nothe June10, 1941 2,388,449 Sundt et a1 Nov. 6, 1945

